1. Field of the Invention
The present invention relates to a fuel desulfurization method, and more particularly, to a fuel desulfurization method that uses a recycled ionic liquid.
2. Description of the Prior Art
Diesel fuel and gasoline are two of the main transportation fuels in use today. Diesel engines typically have great fuel mileage, but diesel fuel is typically derived from crude oil, which often contains sulfur. Therefore, the benefit of high fuel mileage is often offset by increased emissions. Many hybrid cars today running on gasoline can get 50 miles a gallon, which is comparable to what a diesel car can get. Unfortunately, diesel cars burn diesel fuel that typically produces more emissions. What the world desperately needs today is clean burning diesel to avoid greenhouse gas emissions and to protect the environment. Although there have been improvements in diesel engine technology and emissions technology, high sulfur content in diesel still creates pollution.
In 2006, as part of the Clean Air Act, the Environmental Protection Agency (EPA) passed a legislation to limit the sulfur content of roadway diesel fuels to 15 ppm by 2010. This regulation was developed to reduce the negative impact of SOX emissions on the environment. SOX is responsible for acid rains, and is a main component of the industrial smog. However, ultra low sulfur diesel (ULSD) fuel production is currently hampered by inefficient desulfurization technologies that have not changed much in decades.
The current commercial technology for removing sulfur compounds from petroleum fuels is the hydrodesulfurization (HDS). The hydrodesulfurization process typically requires a liquid gas mixture with temperatures ranging from 300 to 400° C. Hydrogen gas is required for the hydrodesulfurization. The high temperature and the high pressure increase the costs, the processing sites sizes and can be explosive. Furthermore, some of the gas and waste heat of the system is lost, which also creates environmental pollution. The process also becomes increasingly inefficient when producing ULSD (15 ppm) fuel, since the production of ULSD (15 ppm) fuel instead of LSD (500 ppm) fuel requires an additional hydrogen consumption of 25 to 45 percent.
Therefore, there is a need for a fuel desulfurization process that is less polluting, more efficient and cost effective.